1. Field of the Invention
This invention is directed to electrophotographic printing and more particularly to an apparatus and method for electrophotographic printing of a lenticular image on a lenticular lens medium.
2. Background
There is an increasing interest in products which provide a 3-dimensional (3-D) visualization of an image. These products include for instance, posters, business cards, point of sale displays, album covers for CD's, book covers, greeting cards, toys, and all types of promotional items.
Generally, such products providing 3-D images use a transparent lenticular lens as a medium for creating the 3-D image. A lenticular lens generally has a front surface consisting of a plurality of parallel semi-cylindrical shaped lenses called lenticules, of which there may be as many as 150 per inch, and a planar rear surface. A lenticular image printed directly on or affixed to the rear surface of the lens results in the creation of a virtual 3-D image viewable from the front surface. Such image may be made to have a variety of characteristics depending upon the particular type of lenticular image which has been printed on or attached to the rear surface of the lenticular lens.
Conventionally, a lenticular lens medium is made of a transparent polymeric material. Polymeric materials lend themselves to manufacture of the lenticular lens medium because of the relative ease by which the lenticular lens medium can be formed by an extrusion process to provide the desired fineness and consistency of the lenticules, transparency, thickness and dimensional stability.
The production of a 3-D device using a lenticular lens medium requires a printing method that can achieve and maintain accurate registration of the lenticular image with the lenticules of a lenticular lens medium, since the quality of the visualized 3-D image depends upon maintaining alignment of the lenticular image as printed on the lenticular lens medium within a portion of a width of a lenticule over the entire length and width of the lenticular lens. The quality of the visualized 3-D image further depends on the density of the lenticular image as printed on the lenticular lens medium.
It is known in the prior art to produce a lenticular based visualization device by first printing the lenticular image on paper or other printable material and then affixing the paper to the rear of the lenticular lens. A problem with this method is that of the amount of time for accurately registering the lenticular image printed on the paper with the lenticules of the lenticular lens. Another problem may arise where the printed-on paper is not uniformly affixed to the lens.
Also, it is known in the prior art to print lenticular images directly on a surface of a polymeric lenticular lens medium using ink by, for example, lithographic offset printing, silk printing, photogravure, typeset printing and inkjet printing. The use of ink requires allowance in the production time for drying of the ink. Further, when printing directly to a polymeric lenticular medium with ink it is necessary to apply an ink absorption/adhesion layer or coating on the lenticular lens medium in order that the ink uniformly adhere to the polymeric medium. Where lithographic printing is used to print a lenticular image on a lenticular medium, substantial investment in set up time and a substantial number of test prints are required in order to initially align and to maintain alignment of the lithographic press with the lenticular medium and thus lithographic printing is economical only for large quantity production runs. Where inkjet printing is employed, the requirement for a high print density (i.e. dots per inch) combined with the need to scan the significant mass of an ink jet cartridge over the surface of the lenticular medium results in a slow throughput of the printed-on lenticular medium.
Electrophotographic printing apparatuses of a type which use a powder toner can print images on paper with high density and high quality at high-speed. Therefore, this type of electrophotographic printing apparatus has been broadly used and commercialized as an output terminal of information processing systems requiring the functions of printing, copying, facsimile and scanning. However, electrophotographic printers which use powder type toners have not heretofore found wide acceptance for printing a lenticular image on a polymeric lenticular lens medium.
What is needed but is not provided by the state of the art is a method for directly printing with a suitable quality and speed, a color lenticular image directly on a polymeric lenticular lens medium such that the creation of a small number of lenticular based visualization devices may be easily, rapidly and economically produced and the cost of the equipment for producing the lenticular based visualization devices be within the economic reach of small printing businesses.